428 
of Acharius, are are all forms of the same ; as, for instance, Lecanora cerina, 
Lecidea luteo-alba, and others of the common Parmelia parietina. As these 
remarks have not been, as far as I know, contradicted, they may now be con- 
sidered established facts. 
Agardh considers Lichens more nearly allied to Fungi than to Algae : he 
remarks, that if Sphserias or Pezizas had a thallus, they would be Lichens, 
and that the same part is all that determines such genera as Calycium, Verru- 
caria, or Opegrapha to be Lichens, and not Fungi. He adds, that all the 
transitions from Algae to to the state of Lichens, which have been detected by 
modern inquirers, are mere degenerations into the form of the Lichen tribe, 
and by no means into Lichens themselves. 
With regard to the arrangement of the genera of Lichens, that of Acha- 
rius has been adopted by lichenologists of this country and of most others : 
but, which is remarkable, not in Sweden ; and it seems probable, from the 
investigations that have lately been instituted, that this celebrated system will, 
like the more general one of Linnaeus, be wholly abandoned. In its room 
every writer upon Lichens has proposed a new one of his own ; Meyer, 
Eschweiler, Wallroth, Agardh, Fries, Chevalier, Fee, have each brought for- 
ward methods of arrangement, of which it may he said, without disparage- 
ment to any of them, that it is impossible at present to say which will be 
eventually adopted. I have taken that of Fries as explained in his Syst. Orb. 
Veg. p. 233, making such additions as I have been able. There are some 
important remarks by Fee upon the thecse of these plants, and the principles 
on which their genera are to be formed, in the Botanische Zeitung for 1835, 
p. 81, 
Fries refers Byssaceee to Lichens with the following short character : — 
“ Aerial, perennial, constantly growing, with a filamentous texture ; consist- 
ing of solid fibres (either few or several glued together with a common bark), 
unchanged and permanent. Fructification homogeneous, growing externally, 
and naked.” Byst. Orb. Veg. 291. Some of these plants appear to be me- 
teoric productions ; on one occasion they are said to have suddenly overrun 
all the leaves of pines on the side next the wind in the neighbourhood of 
Dresden; on another, on the 29th of Aug. 1830, to have in an instant 
spread over the sails and masts of a ship at Stockholm ; and Fries is disposed 
to consider the cobweb-like matter that overruns the grass in the mornings of 
spring and autumn, of this nature, and not of an animal origin. See S. 0. 
Veg. 318. 
The only point to which it is further necessary to advert, is the separation 
of the tribe called Hypoxyla from Lichens. In part, this is composed of 
Opegrapha and other Lichenoid, and of Sphseria and various Fungoid, genera ; 
its character is to discharge a sporuliferous pulp from the nucleus. But it 
seems to be a prevalent opinion that this character is uncertain and unimpor- 
tant, and consequently the supposed tribe will fall back in part into Lichens, 
and in part into Fungi, from which it sprung. Greville, however, adheres to 
the distinction. 
Geography. Pulverulent Lichens are the first plants that clothe the bare 
rocks of newly-formed islands in the midst of the ocean, foliaceous Lichens 
follow these, and then Mosses and Hepaticse. D'Urville Ann. Sc. 6. 54. 
About 800 species are described by Acharius, the number of which is perhaps 
capable of some reduction ; 200 are added by Fee, and great numbers are, no 
doubt, still undiscovered. They are found upon trees, rocks, stones, bricks, 
pales, and similar places ; and the same species seem to be found in many dif- 
ferent parts of the world : thus, the Lichens of North America differ little 
from those of Europe. Fee estimates the number actually known, either in 
herbaria or in books, at 2400. 
